A combustor of a gas turbine has a pilot nozzle and a plurality of main nozzles. As shown in FIG. 22, the main nozzles are divided into a nozzle group A and a nozzle group B, for example. The number of nozzles constituting the nozzle group A is set smaller than the number of nozzles constituting the nozzle group B.
In such a combustor, the nozzle groups used for fuel supply are switched according to the load on the gas turbine. For example, Japanese Unexamined Patent Application, Publication No. Hei-8-312377 discloses a technology in which nozzle groups are smoothly switched by controlling the amounts of fuel supplied to the respective nozzle groups in a nozzle switching period. Specifically, as shown in FIG. 23, when the nozzle group A is switched to the nozzle group B, control is carried out so that the amount of fuel supplied to the nozzle group B is increased, and the amount of fuel supplied to the nozzle group A is reduced by that increased fuel amount. In other words, in the nozzle switching period, the amounts of fuel supplied to the respective nozzle groups are adjusted such that the sum of the amount of fuel supplied to the nozzle group A and the amount of fuel supplied to the nozzle group B becomes constant.
Patent Citation 1:    Japanese Unexamined Patent Application, Publication No. Hei-8-312377